1 The hook

1.1 A recipe that checks the code

A file with a syntax error breaks tally, and nothing finds it before it goes into git. A recipe check compiles every Python file of tally. Python then reports a syntax error at once, without running the code.

Apply the patch to justfile, from the top of the project:

curl -fsSL https://github.com/rahuldave/tally/commit/e1ef40fe88bbf92165b8da067169897e163a59af.diff | git apply --include=justfile

The patch adds the recipe check at the end of the justfile.

just check && echo "the code compiles"

It prints the code compiles, because every file compiles.

Check your files against this move. The command prints nothing when they match, and otherwise shows what differs:

git check e1ef40fe88bb

If you are stuck, this command puts the files of this move in place of yours. A file that you made yourself stays:

git restore --source eb951f747563 --staged -- :/ && git restore --source e1ef40fe88bb --staged --worktree -- :/

@@ -13,3 +13,7 @@ run file:
 # Run the tests
 test:
     uv run python -m unittest discover -s tests -q
+
+# Check that every Python file compiles
+check:
+    uv run python -m py_compile src/tally/*.py

1.2 A hook script

just check works only when someone runs it. A hook runs it every time. git runs the file pre-commit of its folder of hooks before each git commit, and stops the git commit when the file fails. The hook, hooks/pre-commit, has three lines. They name the shell that runs it, say what it does, and run the check. The file comes whole, as a patch.

Apply the patch to hooks/pre-commit, from the top of the project:

curl -fsSL https://github.com/rahuldave/tally/commit/5bd8d5bb524c565e0cfa0cdfb184ca9895203ef1.diff | git apply --include=hooks/pre-commit

Read its last line, just check. It is the whole of what the hook does.

sh hooks/pre-commit; echo "the hook said $?"

The code compiles, so the hook says 0.

Check your files against this move. The command prints nothing when they match, and otherwise shows what differs:

git check 5bd8d5bb524c

If you are stuck, this command puts the files of this move in place of yours. A file that you made yourself stays:

git restore --source e1ef40fe88bb --staged -- :/ && git restore --source 5bd8d5bb524c --staged --worktree -- :/

@@ -0,0 +1,3 @@
+#!/bin/sh
+# Run before each commit: refuse it if the code does not compile.
+just check

1.3 Make it runnable

git runs a hook only if the hook is executable, so we make it executable.

chmod +x hooks/pre-commit

Run the hook by hand on a broken file, and see it fail. Then remove the file:

printf 'def (\n' > src/tally/broken.py; ./hooks/pre-commit; echo "the hook said $?"
rm src/tally/broken.py

The hook says 1, so git would stop the git commit.

Check your files against this move. The command prints nothing when they match, and otherwise shows what differs:

git check 8d19bc56776a

If you are stuck, this command puts the files of this move in place of yours. A file that you made yourself stays:

git restore --source 5bd8d5bb524c --staged -- :/ && git restore --source 8d19bc56776a --staged --worktree -- :/

1.4 Install it

git does not copy hooks with a repository, and does not look in the folder hooks unless it is told to. So each copy of the project installs the hook. A recipe install-hook sets core.hooksPath, the setting of git that names the folder of hooks. The recipe changes the settings of git, so it is a recipe of its own, and not a part of just setup. just setup only runs uv sync, which makes the environment.

Apply the patch to justfile, from the top of the project:

curl -fsSL https://github.com/rahuldave/tally/commit/531ba4ddcb71619b788518683004a96f9574a461.diff | git apply --include=justfile

The patch adds the recipe install-hook, with its comment, at the end of the justfile.

just install-hook && git config core.hooksPath

It prints hooks, so git now runs the hook before each git commit.

Check your files against this move. The command prints nothing when they match, and otherwise shows what differs:

git check 531ba4ddcb71

If you are stuck, this command puts the files of this move in place of yours. A file that you made yourself stays:

git restore --source 8d19bc56776a --staged -- :/ && git restore --source 531ba4ddcb71 --staged --worktree -- :/

@@ -17,3 +17,7 @@ test:
 # Check that every Python file compiles
 check:
     uv run python -m py_compile src/tally/*.py
+
+# Make git run the hooks in hooks/, before each commit. This changes git's config, so it is not part of setup
+install-hook:
+    git config core.hooksPath hooks